1. Field of the Invention
The present invention relates to a self-light emitting device that has an EL element formed over an insulating member and constructed of a luminous organic material (hereinafter referred to as organic EL material) capable of obtaining EL (Electro Luminescence) sandwiched between an anode and a cathode, and to a method of manufacturing an electric appliance having the self-light emitting device as a display unit (a display or a display monitor). It is to be noted that the above-mentioned self-light emitting device is also referred to as an OLED (Organic Light Emitting Diodes).
2. Description of the Related Art
In recent years, the development of a display device (self-light emitting device) using as an EL element a self-light emitting element that utilizes the EL phenomenon of a luminous organic material is proceeding. The self-light emitting device is a self-emissive type device and, hence, unlike a liquid crystal display device, does not need a back light. In addition, the self-light emitting device has a wide angle of view, and therefore is perceived as a prospective display unit for electric appliances.
Note that the EL element is composed of a layer containing an organic compound from which electro luminescence (luminescence generated by applying an electric field) can be obtained (hereinafter referred to as EL layer), an anode layer, and a cathode layer. There are two types of luminescence in an organic compound, one being a luminescence that is generated in returning to a ground state from a singlet excitation state (fluorescence) and the other being a luminescence that is generated in returning to a ground state from a triplet excitation state (phosphorescence). The present invention may be applied to either type of luminescence.
There are two kinds of self-light emitting device: a passive type (simple matrix type) and an active type (active matrix type), and both types are being developed actively. In particular, the active matrix type self-light emitting device is currently attracting much attention. In the EL materials for the EL layer which can be said as the core of the EL element, researches are being made on low molecular based organic EL materials and high molecular based organic EL materials (polymer based). The polymer type organic EL materials are particularly highly regarded since they are easier to handle and have higher heat resistance in comparison with the low molecular based organic EL materials.
A method in which an application is controlled by an electric field and an ink-jet method proposed by Seiko-Epson, Co. can be cited as film deposition methods for the polymer type organic EL materials.
According to the present invention, the same method is used to form the EL layer and a film made of an organic material (organic resin) (the film will hereinafter be referred as a cover layer) that is formed over the EL element and covering the EL element. It is to be noted that the cover layer is a layer made of an organic material and which will be formed over the cathode of the EL element composed of an anode, an EL layer, and a cathode. The provision of this cover layer is effective for the stress relaxation of the TFT or the EL element. Further, the permeation of moisture and oxygen into the EL layer can be prevented, whereby the degradation of the EL layer can be prevented. By further forming a film made of an inorganic material (hereinafter referred to as a barrier layer) on the cover layer, moisture and oxygen can be prevented from permeating into the cover layer or the EL layer.